Date: Tue, 21 Jun 2011 20:27:43 -0700 From: Julian Elischer <julian@freebsd.org> To: Warner Losh <imp@bsdimp.com> Cc: src-committers@freebsd.org, Alan Cox <alc@rice.edu>, Alan Cox <alc@freebsd.org>, svn-src-all@freebsd.org, Attilio Rao <attilio@freebsd.org>, "Bjoern A. Zeeb" <bz@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, svn-src-head@freebsd.org Subject: Re: svn commit: r223307 - head/sys/vm Message-ID: <4E01612F.4080007@freebsd.org> In-Reply-To: <BEDB4F71-8151-4799-9272-8CE79CDA6C17@bsdimp.com> References: <201106191913.p5JJDOqJ006272@svn.freebsd.org> <BBC34F79-FFA7-4A05-83B3-DE17E0AB14D0@FreeBSD.org> <20110622063258.D2275@besplex.bde.org> <BANLkTi=7WnYPQRwE4Hi472DuJz91d1sK=g@mail.gmail.com> <4E0128FF.6020804@rice.edu> <BEDB4F71-8151-4799-9272-8CE79CDA6C17@bsdimp.com>
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On 6/21/11 7:27 PM, Warner Losh wrote: > > On Jun 21, 2011, at 5:27 PM, Alan Cox wrote: > >> On 06/21/2011 16:09, Attilio Rao wrote: >>> 2011/6/21 Bruce Evans<brde@optusnet.com.au >>> <mailto:brde@optusnet.com.au>>: >>>> On Tue, 21 Jun 2011, Bjoern A. Zeeb wrote: >>>> >>>>> On Jun 19, 2011, at 7:13 PM, Alan Cox wrote: >>>>> >>>>> Hi Alan, >>>>> >>>>>> Author: alc >>>>>> Date: Sun Jun 19 19:13:24 2011 >>>>>> New Revision: 223307 >>>>>> URL: http://svn.freebsd.org/changeset/base/223307 >>>>>> >>>>>> Log: >>>>>> Precisely document the synchronization rules for the page's >>>>>> dirty field. >>>>>> (Saying that the lock on the object that the page belongs to >>>>>> must be >>>>>> held >>>>>> only represents one aspect of the rules.) >>>>>> >>>>>> Eliminate the use of the page queues lock for atomically >>>>>> performing >>>>>> read- >>>>>> modify-write operations on the dirty field when the underlying >>>>>> architecture >>>>>> supports atomic operations on char and short types. >>>>>> >>>>>> Document the fact that 32KB pages aren't really supported. >>>>> contrary to the tinderbox I'd like to point out that all mips >>>>> kernels >>>>> built by universe are broken with a SVN HEAD from earlier today. >>>>> Could you >>>>> please check and see if you can fix it? The errors I get are: >>>>> >>>>> vm_page.o: In function `vm_page_clear_dirty': >>>>> /sys/vm/vm_page.c:(.text+0x18d0): undefined reference to >>>>> `atomic_clear_8' >>>>> /sys/vm/vm_page.c:(.text+0x18d0): relocation truncated to fit: >>>>> R_MIPS_26 >>>>> against `atomic_clear_8' >>>>> vm_page.o: In function `vm_page_set_validclean': >>>>> /sys/vm/vm_page.c:(.text+0x38f0): undefined reference to >>>>> `atomic_clear_8' >>>>> /sys/vm/vm_page.c:(.text+0x38f0): relocation truncated to fit: >>>>> R_MIPS_26 >>>>> against `atomic_clear_8' >>>> Atomic types shorter than int cannot be used in MI code, since >>>> they might >>>> not exist. Apparently they don't exist on mips. jake@ fixed all >>>> their >>>> old uses for sparc4 in ~Y2K. >>> I'm sure they do, they exist in support.S though and may not have the >>> _8 form (they may just have the _char version). I may look at the code >>> again to be sure. >>> >> >> It appears that while mips/include/atomic.h declares the existence >> of atomic_clear_8, mips/mips/support.S doesn't implement it. In >> other words, only support for int's and short's is currently >> implemented, not char's: >> >> # grep atomic_clear mips/mips/support.S >> * atomic_clear_32(u_int32_t *a, u_int32_t b) >> LEAF(atomic_clear_32) >> END(atomic_clear_32) >> * atomic_clear_16(u_int16_t *a, u_int16_t b) >> LEAF(atomic_clear_16) >> END(atomic_clear_16) > > The current crop of atomic*16 and atomic*8 functions have the > restriction that the address must be 32-bit aligned (and it forces > this by aligning to 32-bits silently and then operates on the low 8 > or 16 bits in that word!) > > I'm guessing that this is likely just wrong. Comments? I'm guessing it depends on whether the hardware supports atomic sub-wordline accesses. (mind you it's getting really hard to work out what a wordline means these days) > > Warner >
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